Hormone Levels in Womb Tied to Autism Risk in Boys: Study
TUESDAY, June 3, 2014 -- Some boys with autism may have been exposed to slightly elevated levels of certain hormones in the womb, a new study suggests -- though it's not clear yet what the finding means.
Researchers found that of 345 boys with and without autism, those with the disorder had somewhat higher levels of steroid hormones in stored samples of their amniotic fluid. Specifically, they had elevated levels of four sex hormones, including testosterone and progesterone, and the stress hormone cortisol.
Experts said it's not yet clear what to make of the results, published online Tuesday in Molecular Psychiatry. And, it's important to note that the study doesn't prove that the elevated hormone levels caused autism, only that there appeared to be a connection between autism and higher levels of steroid hormones.
"This doesn't say anything about the role of steroid hormones in autism development," said Alycia Halladay, senior director of environmental and clinical sciences for the advocacy group Autism Speaks.
But the findings do raise questions for further research, according to Halladay, who was not involved in the research.
It's possible that steroid hormones, themselves, are the culprit, since research suggests they affect fetal brain development, according to Simon Baron-Cohen, the lead researcher on the new study.
"Elevated steroid levels could directly change gene expression in the brain," said Baron-Cohen, who directs the Autism Research Center at the University of Cambridge in the U.K.
On the other hand, he said, the hormone elevations could be the result of some other, unknown factor.
Autism spectrum disorders refer to a range of neurodevelopmental disorders. These disorders are characterized by social difficulties, communication problems and repetitive behaviors, according to the National Institute of Neurological Disorders and Stroke. In the U.S., an estimated one in 68 children has been diagnosed with autism spectrum disorder, according to the U.S. Centers for Disease Control and Prevention.
For the study, the researchers used stored samples from a large pool of Danish women who underwent amniocentesis between 1993 and 1999. Amniocentesis involves drawing a small amount of fluid from the sac around the fetus; it's typically offered to women who are at increased risk of having a baby with a birth defect.
Baron-Cohen's team compared samples from 128 boys who developed autism with those from 217 boys without autism. They said they excluded girls because only a small number had autism, and other factors made it too difficult to compare steroid hormone levels between those girls and typically developing girls.
Among the boys, those with autism tended to have higher prenatal steroid hormone levels.
Still, Halladay noted, the average difference between the groups was small -- and it's hard to know the possible significance. But, figuring out why there was a difference at all might give insight into some causes of the disorder, according to Halladay.
She said that certain environmental exposures may affect steroid hormone levels -- including "endocrine-disrupting" chemicals found in plastics, metal food cans and other everyday products.
But so far, Halladay said, studies have failed to find a link between those chemicals and autism risk.
Both Baron-Cohen and Halladay stressed that the current study's findings have no practical use for now.
"This doesn't mean pregnant women should ask for amniocentesis to have their hormone levels measured," Halladay cautioned.
And, Baron-Cohen said, there are no grounds for treating autism with hormone-blocking drugs.
Another autism expert stressed that the disorder is thought to arise from a complicated mix of genetic vulnerability and environment.
"It's extremely complex, and it's not going to come down to just one factor," said Dana Levy, an assistant professor of child and adolescent psychology at NYU Langone Medical Center in New York City.
Scientists have already linked a few hundred genes to autism, and studies are investigating potential environmental factors -- from toxic chemicals to infections during pregnancy.
"Researchers are coming at this from every angle to try to understand what is happening in autism," Levy said.
Boys are at particular risk, being affected almost five times more often than girls. And that is one of the big mysteries of autism, Levy noted.
Baron-Cohen speculated that his findings hint at one explanation. The elevated hormones in this study included not only testosterone, but precursors to testosterone.
However, everyone said more studies, including studies of girls with autism, are needed before any conclusions can be made.
For now, Baron-Cohen said the results can be seen as more evidence that the origins of autism go back to the womb.
The U.S. Centers for Disease Control and Prevention has more on autism.
Posted: June 2014